Prediction
My predictions, using previous knowledge is that the higher the concentration of Sodium Thiosulphate there is the faster the reaction rate will be.
This is based on the collision theory which I have outlined in Background Knowledge.
In my preliminary work this has always been the case, for example if I used 40 ml of Sodium Thiosulphate and 10 ml of water it was much faster than when I used 10 ml of Sodium Thiosulphate and 40 ml of water.
Background Knowledge
The rate of a reaction depends on two factors.
1) The number of collision per unit time between the reacting species.
2) The fraction of these collisions that are successful in producing a mew molecule.
If two or more molecules collide but are not orientated correctly then no reaction will take place. For a reaction to occur, molecules must collide not only with sufficient energy but with the proper orientation.
This diagram is the reaction between ethane, CH2CH2, and hydrogen chloride, HCl.
In dilute Sodium Thiosulphate there are not so many particles. This means that the chance of the particles colliding, and colliding correctly is much less than if the Sodium Thiosulphate was concentrated.
Apparatus
- Conical flask
- Burettes
- Measuring cylinder
- Funnels
- Thermometer
- Beakers
- Filter paper
- Sodium Thiosulphate
- Hydrochloric acid
- Distilled water
Method
I plan to find my results using the following method:
5 cm3 of Hydrochloric Acid, 40 cm3 of Sodium Thiosulphate and 10 cm3 of distilled water are poured out into two measuring cylinders and then poured into a conical flask, which is placed on top of a piece of filter paper marked with the letter X. The stopwatch will now be started. When the mixture has turned sufficiently cloudy so that the letter X can no longer be seen the stopwatch will be stopped and the time will be recorded. The experiment is repeated with the concentrations of Sodium Thiosulphate and distilled water are changed. The whole procedure is then repeated.
The experiment is repeated until a wide range of results are obtained. A graph can then be drawn representing the results.
Fair Test
In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and sodium thiosulphate will not be mixed up. The amount of HCl will be 5 cm3 each time.
